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Virtual reality helps rebuild face destroyed by fungus

By Aviva Rutkin

(Image&colon; Texas A&M University)

In 2010, a middle-aged Texan man named Billy Crawford went to hospital to check out an odd black dot on his nose. Doctors identified the culprit as an infection of the rare fungus Mucormycosis, which tends to affect people with compromised immune systems. They moved fast, treating Crawford with anti-fungal medication, but in just 4 hours, the disease had eaten away at much of the soft tissue of his face and one of his eyes.

On Friday at the AAAS Annual Meeting in San Jose, California, prosthetics expert Suzanne Verma described how her team restored the shape of Crawford’s face using a pioneering imaging technique and silicone mask design.

To start, Verma and her colleagues at Texas A&M University in Dallas collected CT scans taken before and after the infection. Software merged the two, creating a computer model of the man’s face. The team could then virtually explore the damaged areas of Crawford’s face, develop a custom plan for surgery, and design the prosthesis.

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GPS in surgery

The prosthesis attached to Crawford’s face via a series of magnets implanted in his skin. In order to ensure the mask would fit snugly and that the surgery would be successful, Verma’s team used the virtual models as a road map of Crawford’s face. By laying light-emitting diodes in his face and using them as markers, they were able to digitally track where the surgical instruments were in the physical world. It enabled the surgeon to see exactly where the scalpel was on the virtual face.

This method, called navigational surgery, made the procedure more accurate and efficient, says Verma. Before he died in 2013, Crawford was able to live a more fulfilling life. “This is the best Christmas gift I could ever receive,” he said.

“It’s GPS in the operating room,” Verma says. “Just as we use satellite to find our position on a moving map while driving our car, we use cameras and tracking devices to help us find our place on an anatomical map while operating in real time on a patient.”

Before tools like those used by Verma existed, surgeons often didn’t know exactly what they would run into when they walked into the operating room, says Pravin Patel, a reconstructive surgeon at the University of Illinois at Chicago. Two dimensional images, like those taken by a CT scan, offered an incomplete picture of what the patient looked like in real life.

Skulls in the desert

But since the introduction of modelling tools like these, doctors have found myriad uses for the technology. Patel, for example, now prepares for upcoming procedures by rehearsing on his iPad, looking at the patient’s skull, making virtual cuts, and moving bones around. When the time comes for the real surgery, he has a strong plan already in place.

“Surgery is so much faster for me,” he says. “It’s like assembling prefabricated houses.”

The technique has found a home outside the hospital, too. James Mah, an orthodontist at the University of Nevada, Las Vegas, uses modelling tools to aid forensic investigations. If a skull is found in the desert, he can scan it, search a database for patients with similar bone structure, and make a realistic estimate of what that person looked like.

“You can assume that if people have the exact dental positions, quite likely these two individuals will look very similar,” he says. “It’s like their skull fingerprint.”